1. Field of the Invention
The present invention relates to an electric motor control apparatus, and particularly to an electric motor control apparatus for controlling an electric motor so as to improve current detection accuracy.
2. Description of Related Art
Conventionally, in current detection of an electric motor, a current detection resistor such as a shunt resistor is connected in series with the electric motor and the current detection is performed based on a voltage occurring across this current detection resistor. As means for correcting an offset occurring by characteristic variations in a circuit element constituting this current detection means, a current detection circuit described in JP-A-3-186477 is proposed. The current detection circuit described in JP-A-3-186477 is a circuit for correcting an offset by associating a current detection signal detected when an electric motor is not driven with a state in which an electric motor current is zero.
Further, JP-A-10-132869 describes a current detection apparatus includes a bridge circuit including three switching element groups and shunt resistors connected to common sides of the switching elements located on negative sides of two of the switching element groups. In the current detection apparatus of JP-A-10-132869, a voltage across the shunt resistor at the time of turning off the switching element connected to the shunt resistor is used for the offset correction. In the offset correction described in JP-A-10-132869, an offset occurring depending on temperature characteristics and characteristic variations in a circuit element constituting current detection means can be corrected in real time.